This invention relates to a combination control for gas burners of a type having a plurality of control valves including a manual main shutoff valve, a thermostatic valve and a diaphragm valve. More particularly, the invention relates to a manual main shutoff valve for a combination control of the above-mentioned type wherein an axially movable valve member is operated by a rotatable valve actuator.
Conventional combination controls for gas burners utilize a plug valve as a manual main shutoff valve to interrupt all gas flow such as when complete shutdown of a gas burner is desired. The plugs and bores in the control casings receiving the plugs are tapered and require costly accurate fitting of the plugs in the casings of combination controls to prevent leakage. Although, a spring may be employed to urge the tapered plug to the small end of the tapered bore receiving the plug, plug valves tend to leak when accidentally subjected to high gas pressures and the plug may even pop out of the bore. High temperature conditions tend to cause the plug to seize in the bore.
To avoid the disadvantages of the plug valve, combination controls have been devised with manually operated means which prevent opening of the thermostatic valve when complete shutoff of gas flow is desired. Combination controls of this type are disclosed in the three Katchka U.S. Pat. Nos. 3,685,730, 3,861,586 and 3,861,587. In these combination controls, a pivotally mounted lever operated by cam means on a rotary actuator forces the thermostatic valve member against its seat regardless of whether or not a thermostatic operator is acting to open the thermostatic valve. The safety valve of each of these controls is also closed at the same time the thermostatic valve is manually closed. The manual shutoff valve arrangements of the aforesaid Katchka patents are not adaptable to the commonly used combination controls of the diaphragm valve type having an electromagnetically operated thermostatic valve which is opened to supply fuel to a pilot burner each time a space thermostat closes in demand for burner operation. Furthermore, this type of combination control does not have a manually main shutoff valve which can interrrupt gas flow to the thermostatic valve.